If you require an email address for eStatements and your member has a wrong email address (and is enrolled in eStatements), the system will do everything to ensure that a paper statement is not mailed (which happens in this case when the email address is marked as incorrect). The next time the member logs on to online banking, they will be presented with a wrong email address prompt and asked to provide a valid email address. A link is provided to the member in this window that takes them directly to the Personal Information Update window, so they can change their email. This change will comply with your credit union's configured rules on personal information changes: direct versus reviewed versus multi-factor authentication (MFA/two-factor). See "Allow maint. of personal info by member (online)" in the last help topic below for where this is configured.
Another solution is to turn off the requirement of an email for eStatements. This is done in via Tool #251 Configure eStatement Settings and Fees. However, if the email address is marked as invalid, no eStatement reminder can be sent, and this member will receive a paper statement.